This invention relates a data transmission system wherein a plurality of transmission modules are connected in a multidrop manner.
It is well known that signal transmission may be effected utilizing building or house wiring or cable for power distribution. A typical example of a multidrop connection scheme is illustrated in FIG. 1, which includes a power distribution cable 1 and a plurality of transmission modules 2 for the transmission and receipt of data. The most serious problem of this kind of system is that in the event that any one of the transmission modules 2 is faulty in a hardware aspect while signals representative of transmission data continued to be supplied to the cable 1, the system becomes disabled as a whole and fails to send signals. In the case that a large number of the modules are installed, it is very difficult to determine which module is working improperly.